Some fixes for the PHY
- Added back timing constraints, otherwise it does not work.
- Fixed RX inversion detection
- It didn’t work at all before
- Now it inverts the RX and waits a few hundred cycles, since it takes a while to take effect
- Added TX CDC variants for testing
- FFSynchronizer
- AsyncFIFOBuffered
- combinatorial connection
- Seems to work best? At least in loopback.